Here's 3 free exercises taken from the Total Body Workout DVD which concentrates on getting your stomachs and waists back in shape!

Side Bends:Exercise for the Waist (External Oblique)

Place the Dyna-Band flat on the floor and stand in the middle of it with your feet shoulder width apart, knees slightly bent and your stomach pulled in.
Take the ends of the band in each hand and slowly stand upright..
Tilt the body to one side, keeping nice and straight. Make sure your shoulder are not tipping forward or back. As you breathe out use your waist (on the opposite side) to pull you back up to an upright position. (Repeat up to 16 times then exercise the other side of your waist).

Oblique Twists with Tricep Extension- for the waist and back of arms

Place the Dyna-Band around your back and under your arms. Take the band between your thumbs and slowly roll down to lie on your back.
Whilst lying on your back, place your feet flat on the floor so your knees are bent. Pull your stomach in and press your lower back firmly into the floor. Take your hands by the side of your head still with the band between your thumbs. Take a deep breath in, as you breathe out, twist and reach one hand to the opposite knee, keeping the other elbow pinned to the floor.
Slowly return to the starting position as you breathe in, then repeat the move to the other knee as you breathe out. (Repeat in sets of 8, doing just one set at first)

Reverse Curls Exercise for the whole stomach & excellent to help bladder control.

Lie on your back bend your knees. Pull your stomach in and press your lower back firmly into the floor then raise your legs until your knees are positioned over your hips.
Place the Dyna-Band across the front of your thighsand hold the band in your hands either side of your legs, with your arms extended - creating a little tension. Take a deep breath in, as you breathe out; pull the knees in towards your chest against the band, keeping the arms extended throughout the exercise.
You should feel a strong pull on your stomach muscles. If you feel any pain in the lower back, stop rest and check your technique. Slowly return to the starting position as you breathe in. (Repeat in sets of 10, doing just one set at first